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Journal of Food Engineering 101 (2010) 365–369
Paper Survey
Gas sensors development using supercritical fluid
technology to detect the ripeness of bananas
C. Steffens, E. Franceschi, F.C. Corazza, P.S.P. Herrmann Jr. , J. Vladimir Oliveira
Advisor : Cheng-Hsin Chuang
Advisee : Hsun-pei Wu
Department of Mechanical Engineering
& Institute of Nanotechnology,
Southern Taiwan University, Tainan, TAIWAN
Date ﹕2010/11/05
1
Outline
• Paper:
Experimental
• Development of electrodes
• Polyaniline synthesis doped with DBSA (PANI–DBSA)
• Film coating deposition
Results and discussion
• Effect of moisture on the response behavior of the tested sensors
• Voltage measurement during the ripeness of bananas
Conclusions
• Furture work
Experimental
• Development of electrodes
Graphite : Water mass ratio
1:4
Fig. 1. Detail of the interdigitate electrode of graphite on tracing paper with 11 fingers.
Polyaniline synthesis doped with DBSA (PANI–DBSA)
•
Two solutions were prepared (solution A and solution B).
solution A
DBSA (0.15 mol)
Stirring
0.3 mol of aniline
Rection 40 hours
500 mL of water
Wash
solution A
Dissolved
APS (0.18 mol)
0℃
100 mL of water
Dried under
vacuum
for 12 hours
Film coating deposition
 In Situ (HCl)
 RESS(rapid expansion of supercritical solutions) :
 CO2= 100 bar , flow rate of 30 mL/min
 solution flow rate of 2 mL/min
 100 lmcapillary tubing.
 2700 psi in liquid pump in pressurized fluid.
 Precipitation:




CO2= 200 bar, flow rate of 20 mL/min
100 lmcapillary tubing.
2900 psi in liquid pump
Drying step: 500 mL of CO2
Results and discussion
Effect of moisture on the response behavior of the tested sensors
Laboratory (air)
10min
Dry nitrogen gas
10min
Fig. 2. Effect of moisture on the response behavior of the tested sensors exposed to cyclic flowing dry nitrogen and laboratory
ambient air.
Voltage measurement during the ripeness of bananas
•
4.5 L chamber, 25℃ , Humidity 60% , Voltage 400mV
=> LabVIEW
AIR
In the air 30 min
into
5 min during 5 days
Sensor
fruits
Voltage measurement during the ripeness of bananas
After 24 s
Fig. 6. Electronic-nose response of in situ, RESS and precipitation sensors to volatile organic compounds
evolved during banana maturation.
Conclusions
• The line patterning technique using graphite was applied to the design and
development of extremely low-cost, disposable interdigitated electrodes.
• Precipitation and RESS proved was to be promising to detect the ripeness
of banana in electronic-nose thus indicating a potential technology.
• In future cost-effective methods for monitoring the maturation of fruits,
avoiding food losses and bringing satisfaction to consumers through
availability of better quality products.
Thank you for your attention!!